memory limit for each user

Is it possible to create a memory limit for each user? I have only found a limit for each domain. How is the memory limit works in ISPConfig? Is there a possibility to connect ISPConfig to e.g. ulimit or cgroup? Is there some experience with this tool?

How do you solved this point for reseller accounts?
We are using a debian 9 and the ISPConfig version 3.1.7